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  • 1
    Online Resource
    Online Resource
    Quality survey of some health supplements containing medicinal herbs tested in Ho Chi Minh in the period of 2015 - 2021
    Vietnamese Journal of Food Control, National Institute for Food Control ; 2022
    In:  Heavy metals and arsenic concentrations in water, agricultural soil, and rice in Ngan Son district, Bac Kan province, Vietnam Vol. 5, No. 3 ( 2022-10-04), p. 516-524
    Details
    In: Heavy metals and arsenic concentrations in water, agricultural soil, and rice in Ngan Son district, Bac Kan province, Vietnam, Vietnamese Journal of Food Control, National Institute for Food Control, Vol. 5, No. 3 ( 2022-10-04), p. 516-524
    Abstract: Many health supplements containing medicinal herbs such as Ginkgo biloba extract, & nbsp;Turmeric extract were tested for quality in Ho Chi Minh City in the period 2015-2021. & nbsp;Testing methods were non-pharmacopoeia methods that accredited methods by Bureau of & nbsp;Accreditation (BoA) or pharmacopoeia methods. The results showed that there were some & nbsp;samples did not meet the quality criteria such as qualitative, quantitative. The quality criteria & nbsp;for safety have been tested such as microbial limits test or the limit of preservatives, heavy & nbsp;metals, and determination of Aflatoxin. & nbsp;
    Type of Medium: Online Resource
    ISSN: 2615-9252
    URL: Article
    DOI: 10.47866/2615-9252/vjfc.3970
    Language: Unknown
    Publisher: Vietnamese Journal of Food Control, National Institute for Food Control
    Publication Date: 2022
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  • 2
    Online Resource
    Online Resource
    Synthesis of Z-scheme g-C3N4/V2O5photocatalyst with high activity under visible light
    Ministry of Science and Technology, Vietnam (VMOST) ; 2021
    In:  Ministry of Science and Technology, Vietnam Vol. 63, No. 11 ( 2021-11-24), p. 42-46
    Details
    In: Ministry of Science and Technology, Vietnam, Ministry of Science and Technology, Vietnam (VMOST), Vol. 63, No. 11 ( 2021-11-24), p. 42-46
    Abstract: Direct Z-scheme g-C3N4/V2O5 photocatalysts were prepared through a sonication-assisted calcination method. The obtained samples were characterised by X-ray diffraction (XRD),Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis-DRS), Scanning electron microscope (SEM), andPhotoluminescence spectroscopy (PL). Oxidations of tetracycline hydrochloride (TC) were employed to evaluate the photocatalytic activities of the obtained g-C3N4/V2O5materials. Different weight ratios (5, 10, 15, and 20%) of g-C3N4/V2O5 loaded composites were prepared, in which a 15% (CV-15) loaded composite was found to show optimal catalytic performance for the reaction. The degradation conversation of TC has achieved approximately 79.67% in CV-15 after a 2-hour reaction. g-C3N4/V2O5 photocatalystwas more active than the individual g-C3N4 and V2O5 materials, which could be attributed to the efficient separation of photogenerated electron-hole pairs shown in the photocatalytic mechanism of TC degradation.
    Type of Medium: Online Resource
    ISSN: 1859-4794
    URL: Issue
    URL: Journal
    URL: Article
    DOI: 10.31276/VJST.63(11DB)
    DOI: 10.31276/VJST.vol(number).page
    DOI: 10.31276/VJST.63(11DB).42-46
    Language: Unknown
    Publisher: Ministry of Science and Technology, Vietnam (VMOST)
    Publication Date: 2021
    SSG: 6,25
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  • 3
    Online Resource
    Online Resource
    Influences of TPU Content on the Weld Line Characteristics of PP and ABS Blends
    MDPI AG ; 2023
    In:  Polymers Vol. 15, No. 10 ( 2023-05-16), p. 2321-
    Details
    In: Polymers, MDPI AG, Vol. 15, No. 10 ( 2023-05-16), p. 2321-
    Abstract: This study aims to explore the effects of Thermoplastic Polyurethane (TPU) content on the weld line properties of Polypropylene (PP) and Acrylonitrile Butadiene Styrene (ABS) blends. In PP/TPU blends, increasing the TPU content results in a significant decrease in the PP/TPU composite’s ultimate tensile strength (UTS) and elongation values. Blends with 10 wt%, 15 wt%, and 20 wt% TPU and pure PP outperform blends with 10 wt%, 15 wt%, and 20 wt% TPU and recycled PP in terms of UTS value. The blend with 10 wt% TPU and pure PP achieves the highest UTS value of 21.85 MPa. However, the blend’s elongation decreases due to the poor bonding in the weld line area. According to Taguchi’s analysis, the TPU factor has a more significant overall influence on the mechanical properties of PP/TPU blends than the recycled PP factor. Scanning electron microscope (SEM) results show that the TPU area has a dimple shape on the fracture surface due to its significantly higher elongation value. The 15 wt% TPU sample achieves the highest UTS value of 35.7 MPa in ABS/TPU blends, which is considerably higher than other cases, indicating good compatibility between ABS and TPU. The sample containing 20 wt% TPU has the lowest UTS value of 21.2 MPa. Furthermore, the elongation-changing pattern corresponds to the UTS value. Interestingly, SEM results present that the fracture surface of this blend is flatter than the PP/TPU blend due to a higher compatibility rate. The 30 wt% TPU sample has a higher rate of dimple area than the 10 wt% TPU sample. Moreover, ABS/TPU blends gain a higher UTS value than PP/TPU blends. Increasing the TPU ratio mainly reduces the elastic modulus of both ABS/TPU blends and PP/TPU blends. This study reveals the advantages and disadvantages of mixing TPU with PP or ABS to ensure that it meets the requirements of the intended applications.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym15102321
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2527146-5
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  • 4
    Online Resource
    Online Resource
    Numerical Study on the Flow Length in an Injection Molding Process with an External Air-Heating Step
    IOSR Journals ; 2017
    In:  International Journal of Engineering Research and Applications Vol. 07, No. 04 ( 2017-04), p. 85-89
    Details
    In: International Journal of Engineering Research and Applications, IOSR Journals, Vol. 07, No. 04 ( 2017-04), p. 85-89
    Type of Medium: Online Resource
    ISSN: 2248-9622 , 2248-9622
    URL: Issue
    URL: Journal
    URL: Article
    DOI: 10.9790/9622-070402
    DOI: 10.9790/9622
    DOI: 10.9790/9622-0704028589
    Language: Unknown
    Publisher: IOSR Journals
    Publication Date: 2017
    detail.hit.zdb_id: 2673348-1
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  • 5
    Online Resource
    Online Resource
    A Study on the Welding Line Strength of Composite Parts with Various Venting Systems in Injection Molding Process
    Trans Tech Publications, Ltd. ; 2017
    In:  Key Engineering Materials Vol. 737 ( 2017-6), p. 70-76
    Details
    In: Key Engineering Materials, Trans Tech Publications, Ltd., Vol. 737 ( 2017-6), p. 70-76
    Abstract: The welding line characteristics of injection molded parts with various venting systems were researched in this paper under the tensile tests of ISO 527. A mold was designed in such a way that specimens with and without a venting system can be developed separately. Both PA66 and PA66 + 30%GF materials were used in this study. Without the venting system, results showed that the weld line strength was only increased when the injection pressure varied from 0.9 MPa to 1.1 MPa, if continuously increasing the injection pressure, the weld line strength will get the negative effect. When the venting system was used, the decrease of the weld line strength with the high injection pressure was eliminated. With the use of 1.3 MPa injection pressure, when increasing the venting gap from 0.02 mm to 0.10 mm, the weld line strength varied from 10.45 MPa to 11.4 MPa with the PA66 material and from 30.8 MPa to 32.95 MPa with the PA66 + 30%GF material. With the case of without venting system, the air trap at the microstructure of weld lines was clearly observed. This trouble was removed when the venting gap value of 0.10 mm was used.
    Type of Medium: Online Resource
    ISSN: 1662-9795
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/KEM.737
    DOI: 10.4028/www.scientific.net/KEM.737.70
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2017
    detail.hit.zdb_id: 2073306-9
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  • 6
    Online Resource
    Online Resource
    WAAM Technique: Process Parameters Affecting the Mechanical Properties and Microstructures of Low-Carbon Steel
    MDPI AG ; 2023
    In:  Metals Vol. 13, No. 5 ( 2023-04-30), p. 873-
    Details
    In: Metals, MDPI AG, Vol. 13, No. 5 ( 2023-04-30), p. 873-
    Abstract: This study surveys the influences of travel speed, voltage, and intensity on the characteristics of low-carbon steel samples generated by the Wire Arc Additive Manufacturing (WAAM) technique. The results indicated that the WAAM samples have isotropy grain shape, with grain size number values varying from about 8 to 12. Interestingly, the WAAM sample achieves better mechanical properties with a higher ultimate tensile strength (UTS) value and higher elongation at break value than the original wire. The UTS value of the WAAM sample is 21–40% higher than the original steel wire. The WAAM sample with a travel rate of 350 mm·min−1, a voltage of 24 V, and an electrical intensity of 120 A reaches the highest UTS value of 694 MPa. The WAAM sample with a travel rate of 400 mm·min−1, a voltage of 22 V, and an electrical intensity of 170 A gains the lowest UTS value of 599 MPa. Moreover, the elongation values oscillate around 41–57%, two or three times higher than the original steel wire. SEM microstructure reveals a ductile fracture surface with dimples of the samples after the tensile test, indicating the toughness of the samples. The fracture surface also shows the equiaxial shape and grain size of the WAAM samples. According to Taguchi analyses, the travel rate factor greatly impacts grain size. The voltage factor has the highest effect on the UTS value. The intensity factor has the most significant impact on the elongation value.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met13050873
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662252-X
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  • 7
    Online Resource
    Online Resource
    Trajectory Strategy Effects on the Material Characteristics in the WAAM Technique
    MDPI AG ; 2023
    In:  Micromachines Vol. 14, No. 4 ( 2023-04-08), p. 827-
    Details
    In: Micromachines, MDPI AG, Vol. 14, No. 4 ( 2023-04-08), p. 827-
    Abstract: The wire Arc Additive Manufacturing (WAAM) technique has evolved into a cutting-edge 3D printing technique. This study surveys the influences of trajectory on the characteristics of low-carbon steel samples generated by the WAAM technique. The results show that the grains in the WAAM samples are isotropic, with grain size numbers ranging from 7 to 12. Strategy 3, with a spiral trajectory, has the smallest grain size, while strategy 2, with a lean zigzag trajectory, has the largest. The variations in grain size are caused by differences in heat input and output during the printing process. The WAAM samples achieve a significantly higher UTS value than the original wire, demonstrating the WAAM technique’s benefit. Strategy 3, with a spiral trajectory, achieves the highest UTS value, 616.5 MPa, 24% higher than the original wire. The UTS values of strategy 1 (horizontal zigzag trajectory) and strategy 4 (curve zigzag trajectory) are comparable. WAAM samples have significantly higher elongation values than the original wire, with only 22% elongation. The sample with the highest elongation value, 47.2%, was produced by strategy 3. Strategy 2 has an elongation value of 37.9%. The value of elongation is proportional to the value of UTS. WAAM samples have average elastic modulus values of 95.8 GPa, 173.3 GPa, 92.2 GPa, and 83.9 GPa, corresponding to strategies 1, 2, 3, and 4. Only a strategy 2 sample has a similar elastic modulus value to the original wire. All samples have dimples on the fracture surface, indicating that the WAAM samples are ductile. These fracture surfaces’ equiaxial shape corresponds to the original microstructure’s equiaxial shape. The results provide the optimal trajectory for the WAAM products is the spiral trajectory, while the lean zigzag trajectory gains only modest characteristics.
    Type of Medium: Online Resource
    ISSN: 2072-666X
    URL: Article
    DOI: 10.3390/mi14040827
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2620864-7
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  • 8
    Online Resource
    Online Resource
    Internal Gas-Assisted Mold Temperature Control for Improving the Filling Ability of Polyamide 6 + 30% Glass Fiber in the Micro-Injection Molding Process
    MDPI AG ; 2022
    In:  Polymers Vol. 14, No. 11 ( 2022-05-30), p. 2218-
    Details
    In: Polymers, MDPI AG, Vol. 14, No. 11 ( 2022-05-30), p. 2218-
    Abstract: In micro-injection molding, the plastic filling in the cavity is limited by the frozen layer due to the rapid cooling of the hot melt when it comes into contact with the surface of the cavity at a lower temperature. This problem is more serious with composite materials, which have a higher viscosity than pure materials. Moreover, this issue is also more serious with composite materials that have a higher weight percentage of glass filer. In this article, a pre-heating step with the internal gas heating method was used to heat the cavity surface to a high temperature before the filling step to reduce the frozen layer and to improve the filling ability of the composite material (polyamide 6 + 30% glass fiber) in the micro-injection molding process. To heat the cavity surface, an internal gas-assisted mold temperature control (In-GMTC) system was used with a pulsed cooling system. We assessed different mold insert thicknesses (t) and gaps between the gas gate and the heating surface (G) to achieve rapid mold surface temperature control. The heating process was observed using an infrared camera, and the temperature distribution and the heating rate were analyzed. Thereafter, along with the local temperature control, the In-GMTC was used for the micro-injection molding cycle. The results show that, with a gas temperature of 300 °C and a gas gap of 3.5 mm, the heating rate reached 8.6 °C/s. The In-GMTC was also applied to the micro-injection molding process with a part thickness of 0.2 mm. It was shown that the melt flow length had to reach 24 mm to fill the cavity completely. The results show that the filling ability of the composite material increased from 65.4% to 100% with local heating at the melt inlet area when the gas temperature rose from 200 to 400 °C with a 20 s heating cycle.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym14112218
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2527146-5
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  • 9
    Online Resource
    Online Resource
    Numerical Study on Local Heating for Thin-Walled Product by External Air Heating
    Trans Tech Publications, Ltd. ; 2019
    In:  Materials Science Forum Vol. 971 ( 2019-9), p. 21-26
    Details
    In: Materials Science Forum, Trans Tech Publications, Ltd., Vol. 971 ( 2019-9), p. 21-26
    Abstract: Gas-assisted mold temperature control (GMTC) is a new technique in the field of mold temperature control. It enables rapid heating and cooling of the cavity surface during the injection molding process. In general, the goals of mold temperature control are to increase the mold surface to the target temperature before filling of the melt and to cool the melt to the ejection temperature. In this paper, dynamic mold temperature control is used for a thin-walled molding part as the temperature distribution and the heating rate are observed. The heating step of DMTC is achieved via hot-air flow directly to the thin-walled area. The results show that the heating rate reached 7.0 °C/s and that the temperature of the mold surface increased from 25 °C to greater than 165 °C within 20 s. A comparison showed that the difference between the simulation and experiment temperatures was less than 5.0 °C. Thus, this method can be used to accurately predict the outcome of a heating step before the actual process is carried out.
    Type of Medium: Online Resource
    ISSN: 1662-9752
    URL: Issue
    URL: Article
    DOI: 10.4028/www.scientific.net/MSF.971
    DOI: 10.4028/www.scientific.net/MSF.971.21
    Language: Unknown
    Publisher: Trans Tech Publications, Ltd.
    Publication Date: 2019
    detail.hit.zdb_id: 2047372-2
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  • 10
    Online Resource
    Online Resource
    Enhancing the Fatigue Strength of the Weld Line in Advanced Polymer Injection Molding: Gas-Assisted Mold Temperature Control for Thermoplastic Polyurethane (TPU) Composites
    MDPI AG ; 2023
    In:  Polymers Vol. 15, No. 11 ( 2023-05-25), p. 2440-
    Details
    In: Polymers, MDPI AG, Vol. 15, No. 11 ( 2023-05-25), p. 2440-
    Abstract: This study presents an innovative approach to enhancing weld line strength in advanced polymer injection molding through applying gas-assisted mold temperature control, significantly increasing mold temperature beyond typical values observed in conventional processes. We investigate the effects of various heating times and frequencies on the fatigue strength of Polypropylene (PP) samples and the tensile strength of Acrylonitrile Butadiene Styrene (ABS) composite samples at different Thermoplastic Polyurethane (TPU) percentages and heating times. Using gas-assisted mold heating, mold temperatures exceeding 210 °C are achieved, which represents a significant advancement compared to the standard mold temperatures of less than 100 °C. As a result, the fatigue strength of the PP sample with mold heating at 15 s shows a remarkable increase of up to 5.4 times at 5 Hz compared to the sample without mold temperature control. Moreover, ABS/TPU blends with 15 wt.% TPU exhibit the highest ultimate tensile strength (UTS) value of 36.8 MPa, while blends with 30 wt.% TPU have the lowest UTS value of 21.3 MPa. This advancement demonstrates the potential for improved welding line bonding and fatigue strength in manufacturing. Our findings reveal that increasing the mold temperature before injection results in higher fatigue strength in the weld line, with the TPU percentage having a more significant influence on the mechanical properties of ABS/TPU blends than heating time. The results of this study contribute to a deeper understanding of advanced polymer injection molding and offer valuable insights for process optimization.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    URL: Article
    DOI: 10.3390/polym15112440
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2527146-5
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